#!/bin/bash

STATUS_FILE="/tmp/dnsmasq-ip-mac.status"

# Script for dnsmasq lease-change hook.
# Maintains the above file with a IP address/MAC address pairs,
# one lease per line. Works with IPv4 and IPv6 leases, file is
# atomically updated, so no races for users of the data.

action="$1"
mac="$2"   # IPv4
ip="$3"

if [  -n "$DNSMASQ_IAID" ]; then
  if [ -z "$DNSMASQ_MAC" -a "$action" = "old" ]; then
       # MAC not known by dnsmasq, probably due to restart.
       exit 0;
  fi
  mac="$DNSMASQ_MAC"   # IPv6
fi

if [ "$action" = "add" -o "$action" = "old" -o "$action" = "del" ]; then
  if [ -f "$STATUS_FILE" ]; then
    sed "/^${ip//./\.} / d" "$STATUS_FILE" > "$STATUS_FILE".new
  fi
  if [ "$action" = "add" -o "$action" = "old" ]; then
    echo "$ip $mac" >> "$STATUS_FILE".new
  fi
  mv  "$STATUS_FILE".new "$STATUS_FILE" # atomic update.
fi